The invention relates generally to contactors, and more particularly, to porous membrane contactors configured for use in a dehumidification system.
Membrane contactors allow a gaseous phase and a liquid phase, to exchange mass and heat between the phases, without dispersing one phase into the other. A common use for a membrane contactor is the removal or dissolution of gases in a liquid. Examples of conventional contactors include packed towers, flat panel membrane contactors, and tubular contactors. In conventional systems, membrane contactors are operated with an aqueous fluid flow adjacent one side of the hydrophobic membrane, and a gas applied to the other side of the membrane. Because the membrane is hydrophobic, the membrane will not allow liquid water to pass through the pores into the gas side of the membrane. By adjusting the vapor pressure of the gas in contact with the membrane, gases, such as water vapor for example, can be selectively removed or dissolved into the liquid.
The effectiveness of a dehumidification system is dependent on the efficiency of the membrane contactor. Several problems exist with conventional contactors. For example, condensation may form on the gas side of the membrane and individual gas and liquid flows cannot be varied independently over wide ranges. In addition, the heat and mass transfer between the liquid and the gas within the contactor occur at different rates, thereby limiting the efficiency of the contactor. If the heat transfer rate is faster than the rate of mass transfer, the temperatures of the hygrospcopic material stream and the air stream will equalize quickly, thereby decaying the mass transfer potential. If the mass transfer rate is faster than the rate of heat transfer, the heat of absorption will diminish the temperature difference between the hygroscopic material stream and the air stream decaying the heat transfer potential. Therefore, to allow for use of porous membrane contactors in dehumidification applications, the membrane contactor design needs to be optimized to balance the heat and mass transfer rates to optimize performance.